Copying detail from one side of an object to another?
This method only works for objects derived from uniform/regular shapes:

First select all vertices you want copied:



Then Shift+D to duplicate, P -&gt; Separate by selection to separate new that part. 

Go back into object mode, select the new part and rotate 90 degrees (if its a cube) to the face you want it on.



Duplicate rotate the new object to other positions you want it on.



Select the original object, go into edit mode and delete the faces that are now occupied by the new objects



Back in object mode, select everything and press Ctrl+J to join them back into one object.

Now press A to select all, W -&gt; Remove Doubles to remove the duplicated vertices and join new faces back together with the original object



And you are done!